There were some other noteworthy findings. Men are much more likely to have an oral HPV infection than women (10.1 percent vs. 3.6 percent). And people who have had more sex partners and more frequent sex are more likely to be positive for HPV.

Merck and GlaxoSmithKline make vaccines against HPV. The vaccine is recommended for girls and, recently, boys to guard against cancers of the cervix and anus, as well genital warts.

But the vaccines aren't approved to prevent oral cancers. And the researchers note that the vaccines' effectiveness against oral HPV infections is "unknown, and therefore vaccination cannot currently be recommended" to prevent oral cancers.

Ohio State's Dr. Maura Gillison, lead author of the paper, has served as a consultant to both Merck and Glaxo. Merck was one of the funders the study.

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